Re: Human Genome May Be Longer Than Expected

Stephen E. Jones (
Sun, 01 Aug 1999 21:44:04 +0800


Here is an article from the New York Times at:

which is claiming that the human genome might have a billion more genes
than previously thought. If that is true, what becomes of claims that we
share 98% of our genes with chimps? Doesn't this show that we would
have to sequence both ours' and the chimps' genomes to know for sure?

And what if it transpires that at the end of it all, that we have millions of
genes that have no homologues in chimps? That would be a powerful
argument against a total naturalistic continuity, and for the intervention of
an Intelligent Designer in the making of humans.

I like the implication that humans are just a fruit-fly that has had two
"evolutionary accidents":

"Humans are known to have four versions of many genes of which a single
version is found in Drosophila, suggesting that a fruit fly-type genome has
been duplicated twice, in two evolutionary accidents, to form a human-type


August 1, 1999

Human Genome May Be Longer Than Expected



The human genome may be as much as four billion chemical units in length,
one-third larger than previously thought, according to new calculations by
Celera, a company that has undertaken a project to decode the genome by

The new estimate of genome length suggests that the number of human
genes is likely to lie at the higher end of the range usually quoted -- 60,000
to 100,000. The new figure also raises questions whether Celera and its
rival, a public consortium that includes the National Institutes of Health,
can finish decoding, or sequencing, a much larger-than-expected genome
under the tight deadlines each has announced.

Each gene carries one or more instructions, and the genome, the full DNA
tape in which the genes are inscribed, is in effect the operating manual of
the cell. Sequencing the genome -- determining the order of the units in
DNA -- has become a high academic and commercial priority because
knowledge of all human genes should allow every disease to be treated at
the genetic level.

The public consortium had originally planned to complete the human
genome sequence by 2005, but the project became a race when the Celera
Corp., founded last year, announced that it would sequence the genome by
the end of 2001. The consortium has said in response that it will deliver a
90 percent complete draft, containing almost all the genes, by the spring of
next year.

Dr. Mark Guyer, an official at the National Institutes' human genome
project, said that it was hard to evaluate the Celera claim but that the public
consortium had always assumed the genome could be 10 percent to 20
percent longer than the three billion units usually assumed.

Because of recent increases in DNA sequencing capacity, Guyer said, the
consortium could still reach its goals even if the genome proved to be 20
percent larger.

Celera, of Rockville, Md., arrived at its larger estimate in a pilot test for its
human genome sequencing. The company has joined with Dr. Gerald M.
Rubin of the University of California at Berkeley to sequence the genome
of the Drosophila fruit fly, an important laboratory organism.

Having started in May, Celera has now sequenced 500 million units of
Drosophila DNA, enough to conclude that the organism's genome is
probably 20 percent to 25 percent longer than the 120 million units
previously thought. A genome must be sequenced 10 times over to
determine its order of units accurately, and Celera will need to sequence
another billion units to complete the Drosophila genome.

If the underestimate with Drosophila and other species is also true of the
human genome, then its size "may have to be readjusted to as much as 4.0
billion base pairs," the company said, adding that the larger estimate had
been built into its timetable for completing work on the human genome.

Analyzing organisms on the basis of their full genomes, instead of gene by
gene, shows how little biologists know even about species that have been
studied for years. The fruit fly has been a standard laboratory organism for
80 years, but only 2,000 of its genes have been well described. The little
insect has 9,000 to 17,000 genes in its genome, according to an article
being published in the journal Genetics by Dr. Michael Ashburner of
Cambridge University, Rubin and others.

Even with this number of genes, the fruit fly is a highly efficient organism
compared with yeast, Rubin said. Yeast is a single-celled mold, without any
of the complications of multicellular organisms, yet it has 6,000 genes in its
operating manual.

If a fruit fly can be designed and operated with a mere 12,000 genes, say,
why does it take about 100,000 genes for the human organism? Humans
are known to have four versions of many genes of which a single version is
found in Drosophila, suggesting that a fruit fly-type genome has been
duplicated twice, in two evolutionary accidents, to form a human-type

The extra copies are free to develop other functions and also to be put
under different control mechanisms, Rubin said. He explained that an
organism with many tissues may need to use a gene in different ways in
each tissue.

As of July 23, the consortium had completely sequenced 12.2 percent of
the human genome, and had produced a draft sequence for a further 7.4
percent, according to its Web site (
Celera has not declared its progress.



"More than 30 years of experimentation on the origin of life in the fields of
chemical and molecular evolution have led to a better perception of the
immensity of the problem of the origin of life on Earth rather than to its
solution. At present all discussions on principal theories and experiments in
the field either end in stalemate or in a confession of ignorance. New lines
of thinking and experimentation must be tried." (Dose K., "The Origin of
Life: More Questions Than Answers", Interdisciplinary Science Reviews,
Vol. 13, No. 4, 1988, p348)